Hello, I'm a healthcare professional with expertise in cardiology. When discussing the QT interval, it's important to understand that it represents the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle, which is typically measured on an electrocardiogram (ECG). A normal QT interval can vary based on several factors, including age, gender, and heart rate. However, a commonly referenced range for adults is between 320 to 440 milliseconds (ms) at a heart rate of 60 beats per minute (bpm). It's also important to note that the QT interval is typically longer in women than in men and can be influenced by factors such as electrolyte levels, certain medications, and underlying heart conditions. It's crucial to interpret the QT interval in the context of the individual's medical history and current health status, as a prolonged QT interval can be a risk factor for a potentially serious heart rhythm disorder known as Torsades de Pointes, which can lead to sudden cardiac arrest. read more >>

Normal QTc values. QTc is prolonged if > 440ms in men or > 460ms in women. QTc > 500 is associated with increased risk of torsades de pointes. QTc is abnormally short if < 350ms. A useful rule of thumb is that a normal QT is less than half the preceding RR interval.read more >>